It is often desirable to alter the thrust produced by a rocket motor during the rocket's flight. In a liquid fuel or hybrid rocket motor, the amount of thrust produced may be controlled by varying the amount of propellant burned. In a solid fuel rocket motor, varying the amount of propellant burned is often impractical. However, thrust may be controlled by altering the exhaust area of the nozzle. Decreasing the area of the nozzle's throat increases pressure inside the motor and thus boosts thrust.
Devices which permit changes in nozzle throat area throughout the entire flight of a rocket are known. These devices typically contain an electrical control system which communicates with a hydraulic system that operates a movable throat restrictor. Such devices permit both increases and decreases in the nozzle throat area.
However, such extensive control is not always necessary. Moreover, such sophisticated control devices include complicated and delicate electrical and hydraulic parts. These parts may be expensive to obtain, install, and maintain, and they are subject to frequent failures due to the high temperatures and pressures present in operating rocket motors.
Other known devices may be actuated only once during the rocket's flight. These devices include a throat restrictor secured by shear pins, explosive bolts, or similar means. Rockets using such devices are generally provided with a relatively large nozzle throat area at launch. At a selected time during the flight, the throat restrictor is released. The throat restrictor is then urged aftward by the rocket motor's exhaust into the nozzle throat, thereby decreasing the throat's area and boosting thrust.
However, these devices rely substantially on the propellant exhaust gases to move the restrictor into position within the nozzle. Moreover, these devices generally contain no mechanical means for restraining or securing a throat restrictor that reaches the desired position within the nozzle. Either deficiency may prevent reliable, precise, and secure throat restrictor placement within the nozzle.
Thus, it would be an advancement in the art to provide a device for boosting solid fuel rocket motor thrust by actively driving a throat restrictor into the nozzle at a desired time during the rocket's flight.
It would be a further advancement to provide such a device which did not substantially rely on the rocket motor's exhaust gases to position the throat restrictor.
It would be an additional advancement to provide such a device which mechanically locks the throat restrictor into the desired position within the nozzle throat.
Such a device is disclosed and claimed herein.